Polymeric materials heretofore mainly used for optics are polymethyl methacrylate and polycarbonate. However, the former has a problem of high water absorption and the latter is insufficient in birefringence after injection molding. Accordingly, it is becoming difficult for them to meet the requirements for such materials that are becoming increasingly more severe.
In recent years, polymers based on polycyclic norbornene-type monomers have been developed as polymeric materials overcoming the above-mentioned problems. For example, Japanese Patent Application Kokai (Laid-open) No. 60-26024 describes that hydrogenation products of ring-opening copolymers of tetracyclododecenes and norbornenes or ring-opening polymers of tetracyclododecenes are excellent in transparency, water resistance and thermal resistance. Japanese Patent Application Kokai (Laid-open) Nos. 60-168708 and 61-292601 disclose that addition polymers of either tetracyclododecenes or polycyclic norbornene-type monomers having more rings and .alpha.-olefins are excellent in transparency, thermal resistance, chemical resistance, water resistance, etc. Thus, polycyclic norbornene-based polymers have excellent properties for use as optical polymers. However, there are problems in that generally the monomers are hardly available and very expensive and that they are still limited in their variety.